Sha'Carri Richardson crashed out of the 100m heats at the US athletics World Championship trials on Thursday as Olympic silver medallist Fred Kerley made a statement in the men's first round.

Richardson's failure was the biggest surprise on the opening day of the US outdoor championships, the selection meeting for the World Championships to be held at the same Hayward Field venue in Eugene in July.

She had clocked 10.85sec in a runner-up finish in New York two weeks ago. But the outspoken sprint sensation was slow out of the blocks and never a factor in her heat, finishing fifth in 11.31sec -- 23rd quickest overall.

That leaves her looking to the weekend's 200m for another chance at a top-three finish needed to make the team.

It's another setback for Richardson, who sprinted to victory at last year's US Olympic trials in a wind-aided 10.64 but saw her dream of an Olympic medal in Tokyo end after a suspension for testing positive for marijuana use.

Richardson's close friend Aleia Hobbs led the way into the 100m semi-finals, winning her heat in 10.88sec. Terry Twanisha was the second-fastest qualifier, winning her heat in 10.92.

In the men's 100m heats, Kerley posted the fastest time in the world this year of 9.83sec.

He took control early in a heat run in a legal wind of 1.5m/sec, with Cravont Charleston a distant second in 10.07.

Kerley's time improved on the 9.85sec that Ferdinand Omanyala of Kenya posted in Nairobi on May 7.

Reigning world champion Christian Coleman made it safely through, winning his heat in 10.08sec. Bracy Marvin and Elijah Hall-Thompson followed him home, both credited with 10.09sec.

Coleman, 26, has a bye for the worlds as the 2019 champion. But even with his berth assured he said he plans to run every round at trials as he continues to return to peak form after serving an 18-month suspension for missing multiple drug testing appointments.

"Even though the 100m is the shortest race in track and field so it seems easy, I feel like it's super-hard," he said. "There's so many opportunities to mess up."

He said believed he was getting sharper with every race, something he'll have to do to retain his world title next month.

"You've got to be perfect at this level."

Coleman said he wasn't surprised to see Kerley, who first made his international reputation as a 400m runner, emerging as an elite 100m threat.

"If you can run, you can run," Coleman said of the runner who narrowly lost 100m gold at the Tokyo Games last year to Italian Lamont Marcell Jacobs.

Three finals were on the slate on Thursday, the women's hammer, women's long jump and men's discus.

- McLaughlin eases through -

In other events World record-holder and Olympic champion Sydney McLaughlin led the way in the women's 400m hurdles first round, winning her heat in 54.11sec.

The week won't produce another showdown between McLaughlin and reigning world champion Dalila Muhammad, who received a waiver to skip the trials because of a hamstring injury but still expects to exercise her bye for the worlds.

McLaughlin said she was looking forward to renewing the rivalry then, but in the meantime she was pleased with her performance even though it didn't approach the world-leading 51.61 she has posted this year.

"That was a really good race just to see kind of where my fitness was at because I hadn't raced in two weeks," she said.

Reigning world champion Donavan Brazier and Tokyo Olympic gold medallist Athing Mu eased through the first round of the men's and women's 800s.

Brazier won his first-round heat in 1:46.49 to top the qualifiers. The American, who shockingly failed to qualify for the Tokyo Olympics, has been battling bursitis in his right foot and had raced just once outdoors this year.

Mu, who won 800m and relay gold in Tokyo last year, set a blistering early pace in her opener on the way to a victory in 2:01.24.